Ship stabilizers



Jan. 2, 1962 J. BELL ETAL 3,015,298

SHIP STABILIZERS Filed May 4, 1961 3 Sheets-Sheet 1 Jan. 2, 1962 J. BELLETAL 3,015,298

SHIP STABILIZERS Filed May 4, 1961 3 Sheets-Sheet 2 if f f' J. BELL ETALSHIP STABILIZERS Jan. 2, 1962 3 Sheets-Sheet 3 Filed May 4, 1961 UnitedStates Patent 3,015,298 SHIP STABILIZERS John Bell, John Victor Full,and Francis Heron Muirhead, all of Beckenham, England, assignors toMuirhead & Co. Limited, Beckenham, England Filed May 4, 1961, Ser. No.107,851 Claims priority, application Great Britain Mar. 23, 1961 4Claims. (Cl. 114126) This invention relates to improvements in theactuating means for generating lift or torque by means, for example, offins or hydrofoils for the purpose of controlling the motion of avehicle, for example, a ship in the rolling or pitching sense.

Means for actuating stabilising fins are known in which the fin is fixedto a shaft which is caused to oscillate in a desired manner by powermeans within the ship. Other actuating means are known in which the finis adapted for rotating or oscillating about a fixed shaft attached tothe side of the ship by means of hydraulic jacks, rotaly vane actuatorsand the like, these means being located within or adjacent to the finand exterior to the ship.

The aforesaid actuating means are all characterised by a multiplicity ofsliding surfaces to be found in the bearings, plungers, cylinders andthe like, that are essential parts of such means. In fin systemsactuated by power means within the ship, watertight glands are requiredWhere the fin shaft passes through the hull. In hydraulic fin systems inwhich the actuating means is external to the ship there is always therisk of water entering and contaminating the pressure fluid.

Moreover, by reason of the multiplicity of parts employed, the aforesaidsystems are ditficult and costly to manufacture.

An object of the present invention is to provide a simple design ofactuating mechanism which is economical to make and has a minimum ofparts.

A further object is to minimise the wear of surfaces that are inrelative motion.

A still further object is to eliminate or partially eliminate the loadon the bearings on the actuating member.

The invention consists of a movement control fin comprising a shaft forsecuring to the structure the movement of which is to be controlled, afin element mounted on the shaft for oscillatory movement about theshaft axis, a web integral with the shaft and extending into the body ofthe fin element, inflatable means mounted one on each side of the flangebetween the flange and the fin element and fluid passage extending fromwithin the inflatable means to outside the fin element.

The invention will now be further described with reference to theaccompanying drawings in which:

FIGURE 1 is a partly sectional plan view of a fin;

FIGURE 2 is a cross-section of a fin in the neutral position.

FIGURE 3 is a three-dimensional drawing of a fin shaft.

FIGURE 4 is a cross-section of a fin in a tilted position.

FIGURE 5 is a cross-section of a fin showing an alternative actuatingmeans.

FIGURE 6 is a diagrammatic representation ofv a complete shipstabilizer.

FIGURE 7 is another diagrammatic representation of a complete shipstabilizer.

FIGURE 8 is a three-dimensional drawing of a fin shaft embodyingactuating cylinders.

FIGURE 9 is a cross-section of FIGURE 8 on the line BB.

FIGURE 10 is a reproduction of FIGURE 9 showing alternative actuatingmeans.

FIGURE 11 is a plan view partly sectioned of a fin embodying pistonactuating means.

FIGURE 12 is a cross-section of FIGURE 11 on the line C-C.

In the figures like parts are indicated by like numerals whereappropriate.

FIGURE 1 shows a view in plan of a fin and actuating means thereforaccording to the invention and FIG- URE 2 is a cross-section of FIGURE 1on the line AA. In the figures, fin 1 which is of streamline section ismounted for rotation or oscillation on shaft 2. The fin 1 is supportedon shaft 2 by bearings 3 and 4 which engage journals 5 and 6respectively on shaft 2. The shaft 2 is displaced or cranked between thejournalled parts in a forward direction as shown at 7 and web or plate 8extends in a rearward direction. The rear edge 9 of web 8 is enlargedand rounded and the forward edge thereof is faired into shaft part 7.FIGURE 3 is a general view of shaft 2.

Bearings 3 and 4 may be fabricated conveniently from rubber or othermaterial suitable for lubrication by water since the fin is not sealedagainst ingress of the sea. The inboard end of shaft 2 terminates in aflange plate 10 secured to the ships side 11 by bolts 11a. Pin 15cooperating with sector shaped slot 16 constitutes a device for limitingthe movement of the fin.

The fin 1 is constructed in three parts, the inboard part 12 enclosingthe bearing 3, the central part 13 enclosing the web 8 and the outboardpart 14 enclosing bearing 4. These three parts may be convenientlyjoined by means of flanges and through-bolts as shown in the sectionalparts of FIGURE 1. Alternatively part 12 may be inserted (embedded) inthe central part 13.

Referring to FIGURE 2, it is arranged that the axis of rotation of fin 1is on the broken line BB which is arranged to be forward of the centreof pressure of the fin indicated by broken line O-C. Thus, thehorizontal axis of fin 1 will normally align itself with the streamlineflow of Water in which it is immersed. The internal surface of part 13of fin 1 is provided with shaped parts 17, 18 which, together with web8, form wedge or V-shaped spaces therebetween. Within these V-shapedspaces are placed inflatable flexible walled containers 19 and 20respectively shown in FIGURE 2 in the deflated condition. The forwardends of containers 19 and 20 are connected over short tubes to ducts 21and 22 respectively within shaft 2, which ducts are continued throughshaft 2 for the supply of pressure fluid over pipes 23 and 23', onlypipe 23 being visible in FIGURE 1.

It can readily be seen that if pressure fluid is introduced into one ofthe containers, for example container 20 of FIGURE 4 causing it toinflate, the corresponding V- shaped space will be enlarged and sinceshaft 2 is fixed, fin 1 will be tilted upwards until arrested by stoppin 15. Similarly, if container 19 is inflated while container 20 isallowed to deflate, the fin 1 will be urged to the downwardly tiltedposition.

It Will be appreciated that containers 19 and 20 can be of such shapeand be 'so disposed in relation to the centre of pressure of the finthat when the fin is tilted and a stabilizing force is thereby generatedthe internal force at D (FIGURE 4) due to the pressurised container andthat acting externally on the fin can be arranged to be equal andopposite, and hence the load imposed on the fin bearings is cancelled oratleast reduced to a minimum.

Friction of the fin movement is thus practically eliminated and abalance can therefore be obtained between fin lift and the appliedinternal pressure. Use can be made of this balance in the control systemfor operating the fin if so desired. Alternatively, the fins may beoperated in a purely On/Ofi manner by admitting through suitable valvemeans, suflicient pressure fluid to cause the fins of a stabilizer toexecute the full movement allowed by the stops. Alternatively the finlift provided is related to ship speed and consequently ensures smootherand sweeter action of the mechanism. I

Alternatively, by suitably controlling the actuating pressure the liftobtained may be limited to a prescribed value despite an increase inship speed.

FIGURE shows an alternative embodiment in which pressure containers 19and 20 are fabricated from elastic material, for example, rubber that isnot reinforced. The elastic containers 19 and 20 are confined withintheir respective V-shaped cavities by flexible barriers 24 and 25 offlexible fabric or other suitable material which close the extremitiesof the two V-shaped cavities, and further barriers of the same material(not shown) which close each side of each cavity. Thus when a containeris inflated, the aforesaid barriers restrain the container in thelateral and endwise directions while the force acting vertically iseffective in actuating the fin as hereinbefore explained.

The figure shows the fin actuated to the upwards position by theinflated container 20 and it will be seen that barrier 25 is fullyextended while because container '19 is deflated, barrier 24 is slack.The same conditions will obviously apply to the barriers adapted toresist lateral pressure.

When the ship is at rest, as when at anchor, however,

it is desirable to prevent the fin from moving continually back andforth against the stop due to rolling, which may occur undersuchcircumstances. To prevent this it is arranged that the twocontainers are each half-inflated or alternatively one is fully inflatedwith pressure fluid. In the first case the fin will remain more or lesscentral and move only a small amount of each successive roll, neverreaching the stops. In the second case, the fin is held rigidly againstone or other of the stops.

FIGURE 6 illustrates in diagrammatic form. a ship stabilizer employing aplurality of fins according to the invention, in which by way of examplefins 2.5, 26 and 27 are disposed along one side of the ship 31 and fins28, 29' and 39am similarly disposed along the other side. A roll sensingdevice 32, which in known simple form may embody a rate gyroscope,produces a signal proprotional to the velocity of the rolling'motion ofthe ship and operates control valve or valves 33 in known manner toregulate the fioW of pressure fluid in each fin actuating means overtheir respective pipe lines 35-48 in any *desired sequence, the pressurefluid being derived from pumping means 34. Two pipe lines. to each fin(only one being shown in the figure) are required, one for actuation ineach direction.

FIGURE 7'illustrates an alternative arrangement to avoid long pipe runswith consequent inefiiciency particularly when the operating fluid isagas. In the figure which for the purpose of illustrationis similar inmany respects to FIGURE 6, the pumping means 34 supplies pressure fluidto a closed pipe line or ring main 44 conveniently locatednear the sidesof the slip from which short branch pipesare taken to each fin.Interposed in each branch pipe is an electrically operated vlave 41 ofwhich many types are known.

In. this arrangement roll sensing deviceg32 controls 7 switching means42 which in turn operate the electrically operated valve 41 overelectrical circuits 43. It must be understood that the switching means42 may be adapted ;to control the action of the fins in any desiredsequence and alternately in either direction. The ring main 44 shouldbeof suflicient cross sectional area to supply pressure fluid to all thefins withoutappreciable fall inpressure.

FIGURESJVS r0112 illustrate a fin and fin actuating means in which theactuating means comprises two pistons operating in correspondingcylinders. In order to provide adequate actuating force in the limitedspace within the fin which permits only a short stroke the cylinders areof large bore. FIGURES 8, 9 and 10 show the fin supporting shaft 2, 7, 6which is of cranked form carrying a rearwards extending web or plate 8and in these respects is similar to the fin supporting shaft shown inFIGURE 3. The web or plate 8 carries cylinder 45, the open end facingupwards and cylinder 46 facing downwards. FIGURE 9 is a cross section ofFIGURE 8 on the line BB showing piston 47 located in cylinder 45 andpiston 48 in cylinder 46. Pistons 47 and 48 are bonded to the adjacentinside walls of cylinder 45 and 46 respectively with an elastic materialsuch as rubber as shown at 49 and 50.

It will be seen that if pressure fluid, for example oil,

is introduced say to cylinder 46 over duct 21, piston 48 will be forcedoutwards and the elastic bond 50 will be stretched or deformed as shownto permit this movement. When the pressure fluid is released the piston48 will be returned to its normal position in cylinder 46' as theelastic bond 50 returns to the unstretched position. A similar motionwill be imparted to piston 47 when pressure fluid is introduced intocylinder 45 over channel 22. Push rods 51 and 51 transmit the motion'ofpistons 47 and 48 respectively to the fin to cause it to tilt in one orother direction according to which push rod is actuated. Thisarrangement is best suited to a stabiliser operating with a liquidhydraulicifluid under relatively high pressure. a

It is to be understood that the construction is not limited'to bondingthe piston to the cylinder using flexible rubber-like substances. It isequally effective to employ a flexible diaphragm which maybe ofcorrugated metal for this purpose.

FIGURE 10 shows an arrangement of pistons and cylinders more suitablefor pneumatic operation. Pistons 47 and 48 are free to move in cylinders45 and 46 respectively and are given motional stability by the provisionQ of cylindrical extension 52 and 52 which are a sliding fit inextensions 53 and 54 to cylinders 45 and 46. The pistons and cylindricalextensions are provided with 0- rings as shown to form an effectiveseal. Circular rubber rings 55 and 56 of, for example, triangularcrosssection are provided in the bases of cylinders 45 and 46 to cushionthe inward motion of the pistons-and provide additional means ofcentralising the fin. The effort required to move the piston itself isthen relatively small and effective operation of the fin can be achievedusing a compressible fluid such as air as the operating medium withpressure of the order of 30 psi, to psi. depending on the diameter ofthe piston and the fin parameters.

FIGURE 11 is a plan in part section of a fin embodying the pistonactuating means of FIGURES 8, 9 and 10 and FIGURE 12 is a section of thefin on the line 'CC.

Conveniently the fin may be of moulded plastic construction and made intwo parts; the main or inboard part 57 and the outboard part 58. Themain part 57 is provided with a recess 59 in the inboard face to locatethe inboard bearing plate 60 (which is split along its longitudinalcentre line) and a cavity 61 extending from the inboard face to theoutboard face of part 57 to accommodate the central part of finsupporting shaft 2, web 8 and cylinders 45 and 46. The inboard'face oftheoutboard fin part 58 is recessed to accommodate the outboard be'aringplate 66 which is screwedor bonded to the fin part 58, two screws beingshown at 62.

theflange plate 19. The twohalves of bearing plate 60 are assembledround the journalled part 5 of shaft 2 and the main fin part 57 is slidover the outboard end of shaft 2 until bearing plate 6% fits in "therecess 59. The outboard fin part 58 is then passed over the outboardendof shaft 2 so that hearing 4 registers with journal 6. Tierods 63 whichare threaded at each end are passed through holes in the two fin parts,the inboard ends being screwed into bearing plate 60 as shown in FIGURE11. Finally nuts 64 are placed on the outboard ends of tierods 63 andthe fin parts 57 and 58 are rigidlyclamped together. The enlarged holes65 may conveniently be plugged with a suitable sealing compound. Thelengths of push rods 50 and 51 may be adjustable.

Constructional limitations in a fin of normal proportions are such thatthe cylinders are displaced axially Within the fin structure and perfectbalance against the hydrodynamic pressure on the fin is not obtained,but an approximation to this balance is possible and the loading on thefin bearings, as described above is to a consider able extent relieved.

In the practical application of the invention thus set forth, variousdevices may be embodied in substitution for those which are herein shownas illustrating the principles involved, and variations may be made inmany respects without departing from the scope of the invention.

We claim:

1. A movement control fin comprising a shaft for securing to thestructure the movement of which is to be controlled, a fin elementmounted on the shaft for oscillatory movement about the shaft axis, aweb integral with the shaft and extending into the body of the finelement, inflatable means mounted one on each side of the web betweenthe web and the fin element and fluid passages extending from within theinflatable means to outside the iin element.

2. A movement control fin as claimed in claim 1 in which the inflatablemeans are flexible walled containers.

3. A movement control fin as claimed in claim 1 in which the inflatablemeans are piston and cylinder combinations.

4. A movement control fin as claimed in claim 1 in which the shaft iscranked in one direction and the web extends from the cranked part inthe opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS2,628,684 Slatter etval Feb. 11, 1953 2,753,835 Gehrig July 10, 19562,969,035 Foll Jan. 24, 1961 2,991,748 Muirhead et al July 11, 1961

